Process for producing a high density by high velocity compacting

ABSTRACT

A method of producing a body from a particulate or solid material comprises filling a precompacting mould with the material, optionally vibrating the mould, pre-compacting the material and compressing it by at least one stroke with high kinetic energy in order to cause coalescence or high density of the material.

The invention concerns a method of producing a body by coalescence orcompaction to higher density.

STATE OF THE ART

In WO-A1-9700751, an impact machine and a method of cutting rods withthe machine is described. The document also describes a method ofdeforming a metal body. The method utilises the machine described in thedocument and is characterised in that preferably metallic materialeither in solid form or in the form of powder such as grains, pelletsand the like, is fixed preferably at the end of a mould, holder or thelike and that the material is subjected to adiabatic coalescence by astriking unit such as an impact ram, the motion of the ram beingeffected by a liquid. The machine is thoroughly described in the WOdocument.

In WO-A1-9700751, shaping of components, such as spheres, is described.A metal powder is supplied to a tool divided in two parts, and thepowder is supplied through a connecting tube. The metal powder haspreferably been gas-atomized. A rod passing through the connecting tubeis subjected to impact from the percussion machine in order to influencethe material enclosed in the spherical mould. However, it is not shownin any embodiment specifying parameters for how a body is producedaccording to this method.

The compacting according to this document is performed in several steps,e.g. three. These steps are performed very quickly and the three strokesare performed as described below.

Stroke 1: an extremely light stroke, which forces out most of the airfrom the powder and orients the powder particles to ensure that thereare no great irregularities.

Stroke 2: a stroke with very high energy density and high impactvelocity, for local adiabatic coalescence of the powder particles sothat they are compressed against each other to extremely high density.The local temperature increase of each particle is dependent on thedegree of deformation during the stroke.

Stroke 3: a stroke with medium-high energy and with high contact energyfor final shaping of the substantially compact material body. Thecompacted body can thereafter be sintered.

In SE 9803956-3 a method and a device for deformation of a material bodyare described. This is substantially a development of the inventiondescribed in WO-A1-9700751. In the method according to SE 9803956-3, thestriking unit is brought to the material by such a velocity that atleast one rebounding motion of the striking unit is generated, therebounding being counteracted whereby at least one further stroke of thestriking unit is generated.

The strokes according to the method described in WO-A1-9700751, give alocally very high temperature increase in the material, which can leadto phase changes in the material during the heating or cooling. Whenusing according to SE 9803956-3 a counteracting of the rebounding motiongenerating at least one further stroke, this stroke contributes to thewave going back and forth and being generated by the kinetic energy ofthe first stroke, continuing during a longer period. This leads tofurther deformation of the material and with a lower impulse than wouldhave been necessary without the counteracting.

It has now been found that the machine according to these documents doesnot work so well. For example, the time intervals between the strokes,which they mention, are not possible to attain. Further, the documentsdo not comprise any embodiments showing that a body can be formed. Also,the rebounding strokes have proved to result in cracking of thematerial.

OBJECT OF THE INVENTION

The object of the present invention is to achieve a low cost process forefficient production of products from a particulate material or a solidmaterial by coalescence or compaction to a higher density. Theseproducts may be both medical devices such as medical implants or bonecement in orthopaedic surgery, instruments, such as surgical knives, ordiagnostic equipment, or non medical devices such as ball bearings,cutting tools, sinks, baths, displays, glazing (especially aircraft),lenses and light covers. Another object is to achieve a product of thedescribed type.

The object to achieve a higher density is based on the fact that highdensity is a condition for high mechanical properties.

The process should not be limited to using the above described machine.

SHORT DESCRIPTION OF THE INVENTION

It has surprisingly been found that it is possible to compress differentmaterials according to the new methods defined in claims 1 and 5. Thematerial is for example in the form of powder, pellets, grains and thelike and is filled in a mould, pre-compacted and compressed by at leastone stroke. The machine to use in the method may be the one described inWO-A1-9700751 and SE 9803956-3 with a vibration device added to achievevibration of the tool or mould. The material may also be in solid formand be inserted into a mould and subjected to at least one stroke, fromtwo or more sides simultaneously, using two or more striking unitsemitting enough kinetic energy to form the body when striking thematerial, causing coalescence or higher density of the material. In thiscase the machine used comprises at least two opposite striking units.

The method according to the invention may utilise hydraulics in thepercussion machine, which may be constructed on the same principle asthe machine utilised in WO-A1-9700751 and SE 9803956-3. When using purehydraulic means in the machine, the striking unit or units can be givensuch movement as to, upon impact with the material to be compressed,emit sufficient energy at sufficient speed for coalescence to beachieved. This coalescence may be adiabatic. A stroke is carried outquickly and for some materials the wave in the material decay in between5 and 15 milliseconds. The use of hydraulic may also give a bettersequence control and lower running costs compared to the use ofcompressed air.

However, the invention is not limited to using a hydraulic machine. Itmay also be possible to use a spring-actuated or electrically actuatedpercussion machine or a machine using compressed air. Neither is itnecessary to always achieve coalescence. In some instances it issufficient to perform compaction to a higher density.

The optimal machine has a large press for pre-compacting andpost-compacting and at least one small striking unit that can strikewith variable speed. Machines according to such a construction aretherefore probably more interesting to use. Different machines couldalso be used, one for the pre-compacting and post-compacting and one forthe compression.

SHORT DESCRIPTION OF THE DRAWINGS

On the enclosed drawings

FIGS. 1 a and 1 b show schematic cross sectional views of twoembodiments of a machine for deformation of a material in the form of apowder, pellets, grains and the like,

FIGS. 2-5 show flow diagrams illustrating the process according to theinvention and

FIGS. 6- are diagrams showing results obtained in comparative testsdescribed in the following examples.

DETAILED DESCRIPTION OF THE INVENTION

The invention concerns a method of producing a body from particulatematerial. The method comprises the steps of

-   -   a) filling a pre-compacting mould with the material in the form        of powder, pellets, grains or the like,    -   b) vibrating the mould,    -   c) pre-compacting the material at least once with a        pre-compacting means and    -   d) compressing the material in a compression mould by at least        one stroke, where a striking unit emits enough kinetic energy to        form the body when striking the material inserted in the        compression mould with a striking means, causing coalescence or        higher density of the material.

By the use of vibration the particles in the pre-compacting mould willmove closer together, forcing out air or gas from between the particlesand they will orient themselves so as to more easily be compacted.Thereby, already before the pre-compaction starts, a higher density isachieved. The pre-compaction will therefore not start from a looselypacked powder, but from a more densely packed powder. Therefor, fewerpre-compaction strokes may be necessary. Should the vibration continueduring the pre-compacting step, a higher density will be achieved usingthe same pre-compaction pressure.

The higher density achieved during pre-compaction will facilitate thecompression step.

A further advantage is obtained if the material is compressed from twoor more sides simultaneously using two or more striking units.

The pre-compacting mould may be the same as the compression mould, whichmeans that the material does not have to be moved between the steps c)and d). It is also possible to use different moulds and move thematerial between the steps c) and d) from the pre-compacting mould tothe compression mould. This could only be done if a body is formed ofthe particulate material in the pre-compacting step.

The invention also concerns a method comprising the steps of

-   -   a) inserting the solid material in a mould,    -   b) possibly pre-compacting the material at least once with a        pre-compacting means and    -   d) compressing the material in the mould by at least one stroke,        from two or more sides simultaneously, using two or more        striking units emitting enough kinetic energy to form the body        when striking the material, causing coalescence or higher        density of the material.

It is preferable that the pre-compacting means is continuously appliedagainst the material, with the same or a higher pressure, during thecompression d) thereof by the striking unit or units.

By using a machine which can strike the material in the mould from twoopposite directions and also compact from these directions the particlesin the powder will be better oriented, a better contact between theparticles will be achieved and a more efficient welding of the particlesresults. The body obtained is more homogenous than a body produced atthe same energy and pressure applied from only one direction. Advantagesarise from the double-sided treatment both during pre-compaction andduring compression.

The preferred method of producing a body from particulate materialaccording to the invention could be described in the following way.

1) Powder is pressed to a green body with vibration, the body iscompressed by impact to a (semi)solid body and thereafter an energyretention may be achieved in the body by a post-compacting. The process,which could be described as Dynamic Forging Impact Energy Retention(DFIER) involves three mains steps.

-   -   a) Pressuring        -   The pressing step is very much like cold and hot pressing.            The intention is to get a green body from powder. It has            proved most beneficial to perform two compactions of the            powder. One compaction alone gives about 2-3% lower density            than two consecutive compactions of the powder. This step is            the preparation of the powder by evacuation of the air and            orientation of the powder particles in a beneficial way. The            density values of the green body is more or less the same as            for normal cold and hot pressuring.    -   b) Impact        -   The impact step is the actual high-speed step, where a            string unit strikes the powder with a defined area. A            material wave starts off in the powder and interparticular            melting takes place between the powder particles. Velocity            of the striking unit seems to have an important role only            during a very short time initially. The mass of the powder            and the properties of the material decides the extent of the            interparticular melting taking place.    -   c) Energy retention        -   The energy retention step aims at keeping the delivered            energy inside the solid body produced. It is physically a            compaction with at least the same pressure as the            pre-compaction of the powder. The result is an increase of            the density of the produced body by about 1-2%. It is            performed by for instance letting the striking unit stay in            place on the solid body after the impact and press with at            least the same pressure as at pre-compaction, or release            after the impact step. The idea is that more transformations            of the powder will take place in the produced body.

FIG. 1 a shows a machine that compacts and compresses a material fromboth an upper and a lower side. FIG. 1 b shows a corresponding machinethat only can compact and strike from one side. The reference numbersfor similar parts are the same in both FIG. 1 a and FIG. 1 b.

The machine shown in FIG. 1 a comprises an upper and a lower strikingdevice 1 a and 1 b. Each striking device has an impact ram 2 a,bcontaining weights 10 and arranged inside an impact ram housing 11 a,b.The mass of the impact rams can be changed by adjusting the number ofimpact ram weights 10 inside the impact ram 2 a,b. Between the strikingdevices 1 a,b there is a central part including support rods 7connecting upper and lower static press tables 12 a, b through whichupper and lower static pre-compaction press rams 5 a,b pass. On thefigure two side support rods 7 are shown. The machine comprises twofurther front and back rods 7 (not shown on the figure). To thepre-compaction rams 5 a,b an upper and a lower punch 9 a,b areconnected. To the support rods a moulding die table 13 is connectedholding a mould 8 arranged between the upper and lower punches 9 a,b. Avibration device 6 is connected to the moulding die table 13. There isalso a hopper 3 from which particles are fed into the mould 8.

The machine in FIG. 1 b comprises the same parts as the machine in FIG.1 a with the following exceptions. It does not comprise any lower impactdevice 1 b, nor the lower static pre-compaction press ram 5 b or thelower static press table 12 b. The lower punch 9 b is connected to a rigfundament 4.

The process steps are schematically illustrated on FIGS. 2-5. FIGS. 2and 3 show the process without energy retention (with non-DFIERmachines) and FIGS. 3 and 5 with energy retention (with DFIER machines).FIGS. 2 and 4 show uni-cycle processes and FIGS. 3 and 5 multi-cycleprocesses where several strokes are used.

The upper part of FIGS. 2-5 shows a time base and above this thedifferent steps performed. The lower part of the figures comprises adiagram showing the change of some parameters during the process. Thepressure parameter is the atmospheric pressure in the mould.

In the process shown in FIGS. 2 and 3 particulate material is firstfilled in the mould. A sub-atmospheric pressure is achieved and thematerial is compressed with a ram during the pre-compaction step. Theram is removed during the delay and thereafter the pre-compactedmaterial is dynamically forged by being struck one or several times withan impact ram. The material is in this case resistance heated during thestrokes, the applied electrical current being synchronized with thetriggering of the impacts. The vacuum is released and the componentobtained is pressed out, optionally after being compressed further withthe pre-compaction ram.

In the process shown in FIGS. 4 and 5 a sub-atmospheric pressure isachieved and the material is compressed with a ram during thepre-compaction step. The ram is maintained pressing together theparticles during the following steps. Vibration of the particulatematerial is used during pre-compaction. As in the process of FIGS. 2 and3 the material is heated with an electric current during shocking. Thepressure from the pre-compaction ram is maintained after shocking forenergy retention, the vacuum is released and the component obtainedpressed out.

In the above embodiments the pre-compaction mould is the same as thecompression mould. Further, the material from which a body is formed isin particulate form. However, it is also possible to use a solidmaterial. In this case it may not be necessary to use pre-compaction.Depending on the density of the solid material a pre-compaction step maybe of advantage. After the possible pre-compaction the solid material isshocked by two opposite impact rams simultaneously. The same steps aswhen forming a particulate material may be used.

Both when starting with a particulate material and a solid material theforming may be performed by using two opposite impact rams. It is alsopossible to use more than two impact rams such as when a deformationsidewise should be obtained.

The pre-compaction step may comprise one or more compactions. As theparticulate material is vibrated, only one compaction may be necessary.However, several compactions may still give a somewhat higher density.

By using the preferred features of the invention it may be possible toachieve material properties of the same level as those achieved byforging of by using HIP or HIP+forging.

The features which may be modified within the definition of the processof the invention are for instance:

-   -   1) the direction of striking, may be in one two or more        directions,    -   2) the vibration, may be during the pre-compaction step and/or        the compression step and/or the energy retention stage,    -   3) the number of pre-compactions,    -   4) interval between pre-compaction stokes,    -   5) temperature during pre-compaction    -   6) pre-compaction pressure    -   7) the same parameters may be modified for the impact step,    -   8) impact stroke pressure and energy, may be the same or be        different for different strokes,    -   9) post-compaction in one or more steps may be used or not,    -   10) atmospheric pressure in the mould, may be decreased or not,    -   11) use of other gases than air, for instance inert gas or a        reactive gas,    -   12) the temperature of the mould and material, may be increased        and in some instances decreased or may be ambient temperature,    -   13) the material to be formed may be particulate, such as        powder, pellets or grains, or solid,    -   14) electrical current may be used or not,    -   15) the vibration may be modified as to amplitude, frequency or        direction, may be vertical and/or horisontal,    -   16) the pre-compaction mould and compression mould may be the        same or different,    -   17) the number of steps may be modified, some steps may be        repeated several times after repeating an earlier step, more        material may be filled in the mould after pre-compaction or        compression and thereafter pre-compaction and/or compression may        be repeated,    -   18) the relation between the mass of the impact ram or rams, the        mass of the punch or punches and the mass of the material to be        formed may be modified,    -   19) energy retention may be used or not.

The mass m of the striking unit is preferably essentially larger thanthe mass of the material. By that, the need of a high impact velocity ofthe striking unit can be somewhat reduced. When the striking unit hitsthe material 1, this may cause a local coalescence and thereby aconsequent deformation of the material. In any case an increase indensity is obtained. Waves or vibrations are generated in the materialin the direction of the impact direction and these waves or vibrationshave high kinetic energy and will activate slip planes in the materialand also cause relative displacement of the grains of the powder. It ispossible that the coalescence may be an adiabatic coalescence. The localincrease in temperature develops spot welding (inter-particular melting)in the material increasing the density.

The pre-compaction is a very important step. This is done in order todrive out air and orient the particles in the material. Thepre-compaction step is much slower than the compression step, andtherefore it is easier to drive out the air. This is further facilitatedby the use of vibration before or during the pre-compaction. Thecompression step, which is done very quickly, does not have the samepossibility to drive out air. Therefore, the air remaining after thepre-compaction may be enclosed in the produced body, which is adisadvantage. The pre-compaction is performed at a minimum pressureenough to obtain a maximum degree of packing of the particles whichresults in a maximum contact area between the particles. This ismaterial dependent and depends on the softness and melting point of thematerial.

The pre-compacting step in the Examples was performed by compacting withan axial load of about 117680 N. This is done was the pre-compactingmould or the final mould. In all Examples where nothing else is statedthe mould used was a cylindrical mould, part of the tool and having acircular cross section with a diameter of 30 mm. The area of this crosssection is about 7 cm². This means that a pressure of about 1.7×10⁸ N/m²was used. The material may be pre-compacted with a pressure of at leastabout 0.25×10⁸ N/m², and preferably with a pressure of at least about0.6×10⁸ N/m². The necessary or preferred pre-compaction pressure to beused is material dependent and for some materials it could be enough tocompact at a pressure of about 2000 N/m². Other possible values are1.0×10⁸ N/m², 1.5×10⁸ N/m². It may be possible to use lower pressures ifvacuum or heated material is used. The height of the cylindrical mouldis 60 mm.

The compression strokes may emit a total energy corresponding to atleast 100 Nm in the described cylindrical tool, in air and at roomtemperature. Other total energy levels may be at least 300, 600, 1000,1500, 2000, 2500, 3000 and 3500 Nm. Energy levels of at least 10 000, 20000 Nm may also be used. There is a new machine, which has the capacityto strike with 60 000 Nm in one stroke. Of course such high values mayalso be used. And if several such strikes are used, the total amount ofenergy may reach several 100 000 Nm. The energy levels depend on thematerial used, and in which application the body produced will be used.Different energy levels for one material will give different relativedensities of the material body. The higher energy level, the more densematerial will be obtained Different material will need different energylevels to get the same density. This depends on for example the hardnessof the material and the melting point of the material.

The energy level needs to be amended and adapted to the form andconstruction of the mould. If for example, the mould is spherical,another energy level will be needed. A person skilled in the art will beable to test what energy level is needed with a special mould. Theenergy level depends on what the body will be used for, i.e. whichrelative density is desired, the geometry of the mould and theproperties of the material. The striking unit must emit enough kineticenergy to form a body when striking the material inserted in thecompression mould. With a higher velocity of the stroke, morevibrations, increased friction between particles, increased local heat,and increased interparticular melting of the material will be achieved.The bigger the stroke area is, the more vibrations are achieved. Thereis a limit where more energy will be delivered to the tool than to thematerial. Therefore, there is also an optimum for the height of thematerial.

The more a material is compressed by the coalescence technique, thesmoother the surface obtained. The porosity of the material and thesurface is also affected by the method. If a porous surface or body isdesired, the material should not be compressed as much as if a lessporous surface or body is desired.

What has been described above about the energy transformation and wavegeneration also refer to a solid body. In the present invention a solidbody is a body where the target density for specific applications hasbeen achieved.

The striking unit preferably has a velocity of at least 0.1 m/s or atleast 1.5 m/s during the stroke in order to give the impact the requiredenergy level. Much lower velocities may be used than according to thetechnique in the prior art. The velocity depends on the weight of thestriking unit and what energy is desired. The total energy level in thecompression step is at least about 100 to 4000 Nm. But much higherenergy levels may be used. By total energy is meant the energy level forall strokes added together. The striking unit makes at least one strokeor a number of consecutive strokes. The interval between the strokesaccording to the Examples was 0.4 and 0.8 seconds. For example at leasttwo strikes may be used.

The method also comprises pre-compacting the material at least twice. Ithas been shown in the Examples that this could be advantageous in orderto get a high relative density compared to strokes used with the sametotal energy and only one pre-compacting. Two compactions give about1-5% higher density than one pre-compaction depending on the materialused. The increase may be even higher for some materials. Whenpre-compacting twice, the compacting steps are performed with a smallinterval between, such as about 5 seconds. About the same pressure maybe used in the second pre-compacting.

Further, the method may also comprise a step of compacting the materialat least once after the compression step. This has also been shown togive very good results. The post-compacting should be carried out at atleast the same pressure as the pre-compacting pressure, i.e. 2000 N/m².Other possible values are 1.0×10⁸ N/m². Higher post-compacting pressuresmay also be desired, such as a pressure which is twice the pressure ofthe pre-compacting pressure. The pre-compacting value has to be testedout for every material. A post-compacting effects the sample differentlythan a pre-compacting. The transmitted energy, which increases the localtemperature between the powder particles from the stroke, is conservedfor a longer time and can effect the sample to consolidate for a longerperiod after the stroke. The energy is kept inside the solid bodyproduced. Probably the “lifetime” for the material wave in the sample isincreased and can affect the sample for a longer period and moreparticles can melt together. The result is an increase of the density ofthe produced body by about 14% and is also material dependent

When using pre-compacting and/or after compacting, it could be possibleto use lighter strokes and higher pre- and/or after compacting, whichwould lead to saving of the tools, since lower energy levels could beused. This depends on the intended use and what material is used. Itcould also be a way to get a higher relative density.

To get improved relative density it is also possible to pre-process thematerial before the process. The powder could be pre-heated to e.g.˜50-300° C. or higher depending on what material type to pre-heat. Thepowder could be pre-heated to a temperature which is close to themelting temperature of the material. Suitable ways of pre-heating may beused, such as normal heating of the powder in an oven. In order to get amore dense material during the pre-compacting step vacuum or inert gascould be used. This would have the effect that air is not enclosed inthe material to the same extent during the process.

Before processing the polymer could be homogenously mixed withadditives.

The body may according to another embodiment of the invention be heatedand/or sintered any time after compression or post-compacting.

Common post-processing steps are following:

Further, the body produced may be a green body and the method may alsocomprise a further step of sintering the green body. The green body ofthe invention gives a coherent integral body even without use of anyadditives. Thus, the green body may be stored and handled and alsoworked, for instance polished or cut. It may also be possible to use thegreen body as a finished product, without any intervening sintering.This is the case when the body is a bone implant or replacement wherethe implant is to be resorbed in the bone.

It has been shown earlier that better results have been obtained withparticles having irregular particle morphology. The particle sizedistribution should probably be wide. Small particles could fill up theempty space between big particles.

The particulate material may comprise a lubricant and/or a sinteringaid. A lubricant may be useful to mix with the material. Sometimes thematerial needs a lubricant in the mould, in order to easily remove thebody. In certain cases this could be a choice if a lubricant is used inthe material, since this also makes it easier to remove the body fromthe mould.

A lubricant cools, takes up space and lubricates the material particles.This is both negative and positive.

Interior lubrication is good, because the particles will then slip inplace more easily and thereby compact the body to a higher degree. It isgood for pure compaction. Interior lubrication decreases the frictionbetween the particles, thereby emitting less energy, and the result isless inter-particular melting. It is not good for compression to achievea high density, and the lubricant must be removed for example withsintering.

Exterior lubrication increases the amount of energy delivered to thematerial and thereby indirectly diminishes the load on the tool. Theresult is more vibrations in the material, increased energy and agreater degree of inter-particular melting. Less material sticks to themould and the body is easier to extrude. It is good for both compactionand compression.

An example of a lubricant is Acrawax C, but other conventionallubricants may be used. If the material will be used in a medical body,the lubricant need to be medically acceptable, or it should be removedin some way during the process.

Polishing and cleaning of the tool may be avoided if the tool islubricated and if the powder is preheated.

In some cases it may be necessary to use a lubricant in the mould inorder to remove the body easily. It is also possible to use a coating inthe mould. The coating may be made of for example TiNAl or BalinitHardlube. If the tool has an optimal coating no material will stick tothe tool parts and consume part of the delivered energy, which increasethe energy delivered to the powder. No time-consuming lubricating wouldbe necessary in cases where it is difficult to remove the formed body.

For example, one to about six strokes may be used. The energy levelcould be the same for all strokes, the energy could be increasing ordecreasing. Stroke series may start with at least two strokes with thesame level and the last stroke has the double energy. The opposite couldalso be used.

The highest density is obtained by delivering a total energy with onesole stroke. If the same total energy instead is delivered with severalstrokes, a lower relative density is obtained, but the tool is saved.Multi-strokes can therefore be used for applications where a maximumrelative density is not necessary. However, the use of several strokesmay give as high density as one sole stroke, provided the time intervalbetween the strokes is extremely short.

Through a series of quick impacts a material body is suppliedcontinually with kinetic energy which contributes to keep the back andforth going wave alive. This supports generation of further deformationof the material at the same time as a new impact generates a furtherplastic, permanent deformation of the material.

According to another embodiment of the invention, the impulse, withwhich the striking unit hits the material body, decreases for eachstroke in a series of strokes. Preferably the difference is largebetween the first and second stroke. It will also be easier to achieve asecond stroke with smaller impulse than the first impulse during such ashort period (preferably approximately 1 ms), for example by aneffective reduction of the rebounding blow. It is however possible toapply a larger impulse than the first or preceding stroke, if required.

When the material inserted in the mould is exposed to the coalescence, ahard, smooth and dense surface is achieved on the body formed. This isan important feature of the body. A hard surface gives the bodyexcellent mechanical properties such as high abrasion resistance andscratch resistance. The smooth and dense surface makes the materialresistant to for example corrosion. The less pores, the larger strengthis obtained in the product. This refers to both open pores and the totalamount of pores. In conventional methods, a goal is to reduce the amountof open pores, since open pores are not possible to get reduced bysintering.

It is important to admix powder mixtures until they are as homogeneousas possible in order to obtain a body having optimum properties.

A coating may also be manufactured according to the method of theinvention. When manufacturing a coated element, the element is placed inthe mould and may be fixed therein in a conventional way. The coatingmaterial is inserted in the mould around the element to be coated, byfor example gas-atomizing, and thereafter the coating is formed bycoalescence. The element to be coated may be any material formedaccording to this application, or it may be any conventionally formedelement Such a coating may be very advantageously, since the coating cangive the element specific properties.

A coating may also be applied on a body produced in accordance with theinvention in a conventional way, such as by dip coating and spraycoating.

It is also possible to first compress a material in a first mould by atleast one stroke. Thereafter the material may be moved to another,larger mould and a further polymer material be inserted in the mould,which material is thereafter compressed on top of or on the sides of thefirst compressed material, by at least one stroke. Many differentcombinations are possible, in the choice of the energy of the strokesand in the choice of materials.

The invention also concerns the product obtained by the methodsdescribed above.

By the use of the present process it is possible to produce large bodiesin one piece. In presently used processes involving casting it is oftennecessary to produce the intended body in several pieces to be joinedtogether before use. The pieces may for example be joined using screwsor adhesives or a combination thereof.

A further advantage is that the method of the invention may be used onpowder carrying a charge repelling the particles without treating thepowder to neutralize the charge. The process may be performedindependent of the electrical charges or surface tensions of the powderparticles. However, this does not exclude a possible use of a furtherpowder or additive carrying an opposite charge. By the use of thepresent method it is possible to control the surface tension of the bodyproduced. In some instances a low surface tension may be desired, suchas for a wearing surface requiring a liquid film, in other instances ahigh surface tension is desired.

Here follow some Examples to illustrate the invention.

The Examples will present and illustrate how different parameters can bevaried to increase the relative density of metal, ceramic and polymersamples processed with the present process. Stainless steel is thematerial tested in all studies except in the powder height-, theoreticaldensity-, powder hardness- and melting temperature studies. See table 1for technical data of the stainless steel used.

The sample dimensions are the same for all studies except in thecollision area study where two sample dimensions are used. TABLE 1Technical data of stainless steel. Properties Stainless steel 316L 1.Particle size (micron) <150 2. Particle distribution (micron) 0.60 wt% > 150 42.70% < 45 3. Particle morphology Irregular 4. Powderproduction Water atomised 5. Crystal structure FCC 6. Theoreticaldensity (g/cm³) 7.90 7. Apparent density (g/cm³) 2.64 8. Melttemperature (° C.) 1427 9. Sintering temperature (° C.) 1315 10.Hardness (HV) 160-190

The samples produced are in the form of a disc with a diameter of ˜30.0mm and a height between 5-10 mm. The height depends on the obtainedrelative density. If a relative density of 100% should be obtained thethickness is 5.00 mm.

In the moulding die (art of the tool) a hole with a diameter of 30.00 mmis drilled. The height is 60 mm. Two stamps are used (also parts of thetool). The lower stamp is placed in the lower part of the moulding die.Powder is filled in the cavity that is created between the moulding dieand the lower stamp. Thereafter the impact stamp is placed in the upperpart of the moulding die and strokes can be performed.

EXAMPLES

1. Powder Height Study

Metal, ceramic and polymer powders were tested in a powder height study.The powder used were stainless steel, hydroxyapatite and UHMWPE. Seetable 2 for properties for the powders tested. TABLE 2 Technical datafor the powders tested in the powder height study. Properties Stainlesssteel 316L Hydroxyapatite UHMWPE 1. Particle size <150 <1 <150 (micron)2. Particle 0.60 wt % > 150 <1 — distribution (micron) 42.70 wt % < 453. Particle Irregular Irregular Irregular morphology 4. Powder Wateratomised Wet chemistry — production precipitation 5. Crystal structureFCC Apatite 50% amorphous 6. Theoretical 7.90 3.15 g/cm³ 0.94 density(g/cm³) 7. Apparent density 2.64 0.6 50 (g/cm³) 8. Melt temperature 14271600 125 (° C.) 9. Sintering 1315 900 — temperature (° C.) 10. Hardness160-190 HV 450 HV R50-70 (Rockwell)Metal

FIGS. 6 and 7 show relative density as a function of impact energy permass and total impact energy, respectively, for samples processed withdifferent powder masses. All samples were tested in the same cylindricalmould but with different powder heights and thus different masses. Thereference mass was 28 g. TABLE 3 Conditions Pressure AtmosphereTemperature Room temperature Energy retention No Material Stainlesssteel Collision area Constant Reference mass 28 gResult

The results show that to reach the same density, less energy per mass isrequired for a body with a greater powder height and thus a higher masscompared to a body with a smaller powder height Approximately the sametotal energy is required to obtain the same density, irrespective of thepowder mass or height.

Ceramic

FIGS. 8 and 9 show relative density as a function of impact energy permass and total impact energy, respectively, for ceramic samplesprocessed with different powder masses. All samples were tested in thesame cylindrical mould but with different powder heights. The referencemass was 11.1 g. TABLE 4 Conditions Pressure Atmosphere Temperature Roomtemperature Energy retention No Meterial Hydroxyapatite Collision areaConstant Reference mass 11.1 gResult

FIG. 8 shows that the three curves follow each other, which means that acertain density is obtained no matter of the specimen shape with respectto impact energy per weight. This is also shown in FIG. 9 where densityis plotted as a function of total impact energy. The curve is shifted tothe left in the diagram for a lower sample mass. It could also be notedthat higher density for the 11.1. g sample never reached the plateaudensity as indicated for the 2.8 and 5.5 g samples. The results showthat the sample mass and powder height in the mould influences thedensity with respect to total impact energy, i.e. a larger sample massneeds more energy in order to obtain a certain density. The results alsoshow that there is a linear relation between mass and density withrespect to impact energy per mass up till at least 271 Nm/g, see FIG. 8.

Polymer

FIGS. 10 and 11 show relative density as a function of impact energy permass and total impact energy, respectively, for polymer samplesprocessed with different powder masses. All samples were tested in thesame cylindrical mould but with different powder heights. The referencemass was 4.2 g. TABLE 5 Conditions Pressure Atmosphere Temperature Roomtemperature Energy retention No Material UHMWPE Collision area ConstantReference mass 4.2 gResult

The curves of smaller masses are shifted to the right or to higherenergy in the density energy graph. Also shift towards lower densitiescould be observed for smaller sample masses.

FIG. 10 shows that a higher density is obtained when the powder heightis increased for a given impact energy per mass. Hence, the maximumdensity is reached at a lower impact energy per mass for a heaviersample. Studying the individual density-energy graph, it could bedivided into three phases. Phase 1 could be characterised as thecompacting phase, phase 2 would be characterised as the plateau phaseand phase 3 characterised as the reaction phase. In the compactionphase, the density-energy curve follows a logarithmic relation with aninitial high compaction rate. The sloop decreases as the energy isincreased and eventually the curve reaches the plateau phase. Theplateau phase is characterised with an almost constant inclination andconstant density. At a certain energy level the density starts toincrease again. This part of the curve is non linear with an initialpositive and increasing derivative. The curve derivative is eventuallydecreasing and the curve is approaching the 100% relative densityasymptotically. Phase 1 and phase 2 could also be seen in the metalcounterparts. The samples of phases 1 and 2 are characterised by opaqueand brittle properties. Entering phase 3, the samples gradually changein properties. A new material phase occurs, first at the outer edges andat the top and bottom end surfaces. This material phase is characterisedas a harder, transparent and with a plastic and fat surface feeling. Forthe smaller mass samples the reaction does not occur gradually butrather direct. The process in phase 3 was also somewhat dramatic andcould be described as a small explosion. Directly after the impactstroke, white smoke was observed coming from the sample, and materialhad extruded out between the stamps and the moulding die. Further, thepressure occurring at the reaction phase proved to be very high whenduring one test the moulding die was cracked open. A larger weightsample was found to densify faster at lower energy per mass levels andthe reaction shift of material phase is occurring gradually rather thandirect as for the small samples. The limited test series of the 12.6 gwas due to the limited powder pillar height of the tool. The insertiondistance was less than the recommended distance of the 30 mm (diameterof stamp). The test was therefore stopped at the impact energy of 2100Nm to eliminate a tool failure. The two large dips in density for the8.4 g sample depend on the sample not holding together and coming out asa powder.

Conclusions

For ceramic powders processed according to the invention the samedensity was obtained independent of the powder height or mass with thesame impact energy per mass. On the contrary, for metal and polymerpowders processed according to the invention, the same density wasobtained independent of the powder height or mass with the same totalimpact energy.

2. Collision Area

FIGS. 12 and 13 show relative density as a function of impact energy andtotal impact energy, respectively, for samples with different collisionsurface areas. TABLE 6 Conditions Pressure Atmosphere Temperature Roomtemperature Energy retention No Material Stainless steel Mass (M) M2/M1= 25 Collision surface S2/S1 = 8 area (S)Result

The curves show a linear relation between collision surface area, shockenergy and pressure. Samples with different diameters will reach thesame density if they are processed with same impact energy per mass.

3. Shrinking

FIG. 14 shows relative density as a function of shrinking in volume %for samples processed according to the invention in comparison withsamples processed with conventional powder metallurgy (PM). All sampleswere sintered after the shocking and pressing step, respectively. FIG.15 shows the comparison between achieved density after sintering for asample processed conventionally and a sample processed according to theinvention (DFIER), respectively. TABLE 7 Conditions Pressure AtmosphereTemperature Room temperature Energy retention No Material Stainlesssteel Material adds Internal lubricant (1.0 wt % Acrawax)Post-processing SinteringResult

The samples processed with Method X reaches a higher density compared toconventional PM processed samples. When samples are sintered after thecompacting step, the material shrink because of internal porosity in thematerial. Shrinking of the material can have negative effects on thestructure and the mechanical properties of the final product.

The curves in FIG. 14 show that the shrinking volume decreases withincreased relative density for all samples. The samples processed withDFIER shrinks more compared with the samples processed conventionally.The reason is probably that the samples processed with DFIER has abetter orientation of particles, and that the energy transmitted duringthe shock phase is stored in the grain boundaries and will be set freeduring sintering. The free energy will increase the driving force tocollapse the porosity and solidify the material during sintering.Samples pressed conventionally have less driving force during sinteringcompared with samples processed with DFIER.

The samples processed with DFIER have high green density beforesintering, which means that the material shrinks less and bettermechanical properties are therefore achieved, compared to a samplecompacted by using conventional pressing. Samples with a low greendensity require a sophisticated and expensive sintering process toremove all porosity in the material. The high green density of samplesprocessed with DFIER make it possible to use a cheaper and simplersintering process to reach full density.

4. Velocity Study

FIG. 16 shows relative density as a function of impact energy forsamples shocked with different impact velocities of the impact ram. Theimpact velocities for the impact ram and punch, respectively, are showedin FIGS. 17, 18 and 19. FIG. 20 shows obtained impact velocity of thepunch for different impact ram masses for the maximum used shock energy,3000 Nm, for all velocity studies. TABLE 8 Conditions PressureAtmosphere Temperature Room temperature Energy retention No MaterialStainless steel Impact velocity of impact ram (m/s) V7 < V6 < . . . < V1Impact velocity of punch VP7 > VP6 > . . . > VP1 (m/s) Equation ofmomentum M_(impact ram) * V = M_(punch) * VPResult

The curves in FIG. 16 show that with a low impact velocity of the impactram the highest density for a specific shock energy is reached quickest.

The differences between the maximum densities for the seven seriesperformed are up to 10 percent. The results indicate that a higherdensity is obtained when the impact ram mass is increased or equivalenta decreased impact velocity for a given energy level per mass. Theeffect is decreased as the energy is increased. The relative density atpre-compacting is to a great extent dependent on the static pressure.

The mass of the impact ram decides the impact velocity of the punchwhich is the velocity that accelerates the powder. A high impact rammass will accelerate a light punch to higher velocities compared with aimpact ram with a lower mass. FIGS. 18 and 19 show that the highestimpact velocity is achieved for the punch accelerated by the greatestand slowest impact ram.

The diagrams show that if the mass of the impact ram increases toinfinity the impact velocity of the ram will reach 0 m/s, which meansthat there is a limit to how great impact ram can be used to obtain ahigh punch velocity.

The relation between the mass of the impact ram and the punch to reachthe highest density was in this study 1:3846.

The material properties of the processed powder and the configuration ofthe tool as well as the material used in the tool have to be consideredto find the optimal mass relation between the impact ram and punch.

5. Multiple Shock Study 1

FIG. 21 shows relative density as a function of the number of shocks forsamples processed with a total shock energy of 3000 Nm and 4000 Nm,respectively. TABLE 9 Conditions Pressure Atmosphere Temperature Roomtemperature Energy retention No Material Stainless steel Total shockenergy Constant for each studyResult

The curves in the diagram show that the highest density is reached forsamples processed with one single shock, compared with the samplesprocessed with the same total energy performed in a multiple shockseries.

We can notice a tendency that the distance between the curves increaseswith increased number of stokes.

6. Multiple Shock-Study 2

FIG. 22 shows the relative density as a function of number of shocks.Four studies were performed. In each study the samples were processedwith one single shock or multiple shocks with a constant energy pershock. TABLE 10 Conditions Pressure Atmosphere Temperature Roomtemperature Energy retention No Material Stainless steel Energy pershock Constant for each studyResult

The curve for the samples processed with the highest energy per shockincreases fastest to a high density compared with the samples processedwith lower energies per shock. The curves show that high densities arereached for shock energies over 50 Nm per shock, which means that thereis a lower limit for the energy per shock when the total energy isdivided into multiple shocks.

7. Heating Study

FIG. 23 shows relative density as a function of impact energy per massfor samples processed in increased temperature. TABLE 11 ConditionsPressure Atmosphere Temperature Increased temperature Energy retentionNo Material Stainless steel Heating temperature 150° C.Result

The samples processed in a temperature above room temperature reachesnearly 100% of density. The curve increases faster to a higher densitycompared with the curve showing the density result for the samplesprocessed in room temperature.

Heating of the powder before and during the DFIER process increases theinitial energy state of the powder. The powder compacting startstherefore from a higher temperature level and the result is a higherfinal density. This means that less energy is required to reach a highenough temperature in the material to achieve spot welding between thepowder particles during the shock phase.

A heating to 150° C. of stainless steel powder results in a relativedensity improvement of ˜2%.

The material properties of the processed powder have to be considered tofind optimal parameter values for the heating

Electric current can be used to heat the powder during DFIER.

8. Vacuum Study

FIG. 24 shows relative density as a function of impact energy per massfor samples processed in vacuum. TABLE 12 Conditions Pressure VacuumTemperature Room temperature Energy retention No Material Stainlesssteel Vacuum −100 PaResult

The curve for the samples processed in vacuum increases faster and thesamples reach a higher density than the samples processed in atmosphericpressure.

When the pressure is decreased between the powder particles thereactivity is increased in the material and spot welding is achieved ata lower process energy, compared with a powder processed in atmosphericpressure.

Samples compacted to high densities in air have pores filled with air.If these samples are sintered after DFIER, the heat during sinteringwill expand the air in the closed pores expanding the material. If thepores have a lower pressure i.e. vacuum or near vacuum, they will notexpand instead they will collapse during sintering and 100% density canbe achieved.

The material properties of the processed powder have to be considered tofind optimal parameter values for processing in vacuum.

9. Impact Direction

FIG. 25 shows relative density as a function of impact energy per massfor samples processed in one or two impact directions. TABLE 13Conditions Pressure Atmosphere Temperature Room temperature Energyretention No Material Stainless steelResult

The samples processed by impacting in two directions increases faster indensity and reaches a higher density compared with samples processed inone impact direction for the same energy. The reason is that the powderprocessed from two directions obtains a better orientation of the powderparticles during DFIER compared with the powder processed from onedirection. A good orientation of the powder particles facilitates thesolidification process.

The material properties of the processed powder have to be considered tofind optimal parameter values for processing powders with two impactdirections.

10. Time Interval Study

FIG. 26 shows relative density as a function of time interval betweentwo consecutive shocks. All samples were shocked two times withdifferent time delays between the shocks. TABLE 14 Conditions PressureAtmosphere Temperature Room temperature Energy retention No MaterialStainless steel Shock energy per 800 Nm Stroke Number of shocks 2Result

The curve shows that the time delay between two shocks should be veryshort to effect the material properly.

The optimal time delay between two shocks depends on the mechanicalproperties of the material processed. Important material properties toconsider are thermal conductivity and acoustic velocity.

11. Energy Retention Study 1

FIG. 27 shows relative density as a function of impact energy per massfor shocked samples in comparison with samples shocked andpost-compacted by energy retention. TABLE 15 Conditions PressureAtmosphere Temperature Room temperature Energy retention Yes MaterialStainless steelResult

The curve showing the result for shocked and post-compacted samplesincreases faster and reaches a higher density compared with the curvefor only shocked samples.

The result of using an energy retention step is that the energytransmitted during the shock phase is retained in the material, and caneffect the sample and increase the metallic bonding and spot weldingamong the powder particles. It is therefore possible to increase therelative density to near 100% by using the post-compacting step.

The material properties of the processed powder have to be considered tofind optimal parameter values for the energy retention.

12. Energy Retention Study 2

FIG. 28 shows relative density as a function of impact energy per massfor samples processed with different time delays between the shock andthe start of the energy retention. TABLE 16 Conditions PressureAtmosphere Temperature Room temperature Energy retention Yes MaterialStainless steelResult

The curve for samples processed with a directly start of the energyretention after the shock step increases fastest and reaches the highestrelative density. The curves show that the time between the shockprocess and the energy retention should be less then 1 s to obtainmaximum effect. 1 second is not an optimum because the optimal timevaries between different material types. The energy retention has lesseffect if the time delay between shock and energy retention increases.

The time duration of the local increase in temperature between thepowder particles after the shock phase is very short. The condition forachieving an effect of the energy retention is that the sample still isin an elevated energy state, which is not the case if the sample alreadyhas cooled down to room temperature. The material properties of theprocessed powder have to be considered to find optimal parameter valuesfor the energy retention.

13. Energy Retention Study 3

FIG. 29 shows relative density as a function of energy retention timefor shocked and post-compacted samples. The curve shows the effect ofthe duration of the energy retention. TABLE 17 Conditions PressureAtmosphere Temperature Room temperature Energy retention Yes MaterialStainless steelResult

The curve shows that the effect of energy retention decreases after afew seconds.

The optimal time for energy retention is depending on the properties ofthe processed material in combination with the sample size. A greatermass will retain the heat for a longer period and it is thereforepossible to increase the energy retention time and still obtain aneffect

14. Pre-Compacting Study 1

FIG. 30 shows relative density as a function of pre-compacting pressure.TABLE 18 Conditions Pressure Atmosphere Temperature Room temperatureMaterial Stainless steelResult

The curve shows that an increase in pre-compacting pressure increasesthe density of the pre-compacted sample.

The pre-compacting pressure on the sample before the shock phase is animportant parameter to consider, because the green density of the samplewill influence the final material properties achieved after a completeDFIER process.

15. Pre-Compacting Study 2

FIG. 31 shows relative density as a function of pre-compact pressure.The curves show the effect of pre-compacting in different surroundingpressures. TABLE 19 Conditions Pressure 1. Atmosphere: (P = 1) 2.Vacuum: (P = 0) Temperature Room temperature Material Stainless steelResult

The curve for samples pre-compacted in vacuum reaches the highestdensity.

The energy necessary to overcome the atmospheric pressure and removingthe air out of the powder at pre-compaction at normal pressure caninstead directly affect the powder at pre-compaction in vacuum.

16. Pre-Compacting Study 3

FIG. 32 shows relative density as a function of impact energy per mass.The samples have been pre-compacted differently by varying the timeduration of the pre-compaction phase. TABLE 20 Conditions PressureAtmosphere Temperature Room temperature Material Stainless steelResult

The curves show that a higher density is reached if the samples arepre-compacted longer than 1 s.

The material properties of the processed powder have to be considered tofind optimal parameter values for the pre-compacting step.

Property Studies

Three property studies were performed: Theoretical density study, powderhardness study and melting temperature study. Powder properties for thepowders are described in tables 21 and 22. TABLE 21 Powder propertiesfor the metals used in the property studies. Properties Ti—6Al—4VTitanium Co—28Cr—6Mo Al-alloy Ni-alloy  1. Particle size <150 <150 <150<150 <150    (micron)  2. Particle — 2 wt % > 150 0.1 wt % > 250 6.57 wt% > 125    distribution balance < 150 3 wt % > 200 50.80 wt % > 106   (micron) 5 wt % > 160 24.25 wt % > 100 5-20 wt % > 100 24.25 wt % > 10020-35 wt % > 63 12.26 wt % > 90 10-25 wt % > 45 6.12 wt % < 90 35 50 wt% < 45  3. Particle Irregular Irregular Irregular Irregular Irregular   morphology  4. Powder — Hydrated Water Water Water    productionatomised atomised atomised  5. Crystal Al stabilises HCP 85% alpha FCCFCC    structure HCP V phase 15% stabilises BCC carbides  6. Theoretical  4.42   4.5   8.5  2.66   8.38    density (g/cm³)  7. Apparent   1.77  1.80   3.4  1.22   2.59    density (g/cm³)  8. Melt 1600-1650 16601350-1450 658 1645    temperature    (° C.)  9. Sintering 1260 1000 1200600 1315    temperature    (° C.) 10. Hardness —  60  460-830 50-10080-200    (HV) Stainless steel Low wrought Properties 316L steelMartensitic steel Tool steel  1. Particle size <150 <150 <150 <150   (micron)  2. Particle 0.60 wt % > 150 3.2 wt % > 150 1.06 wt % > 150 0.4wt % 150-180    distribution 42.70% < 45 79.5 wt % < 150 4.32 wt % > 12524.48 wt % 106-150    (micron) 12.03 wt % > 106 26.68 wt % 75-106 23.59wt % > 75 28.67 wt % 45-75 19.26 wt % > 53 19.77 wt % < 45 9.04 wt % >45 30.70 wt % < 45  3. Particle Irregular Irregular Irregular Irregular   morphology  4. Powder Water atomised Water atomised Water atomisedWater atomised    production  5. Crystal FCC BCC < 900° C. FCC BCC <910° C.    structure FCC > 900° C. FCC > 910° C.  6. Theoretical   7.90  7.75   7.73   7.75    density (g/cm³)  7. Apparent   2.64   2.87  3.37   2.55    density (g/cm³)  8. Melt 1427 1540 1427 1350-1450   temperature    (° C.)  9. Sintering 1315 1230 1230 1315    temperature   (° C.) 10. Hardness 160-190 130-280 180-330  207-241    (HV)

TABLE 22 Powder properties for the ceramics used in the propertystudies. Properties Silicone nitride Hydroxyapatite Alumina Zirconia  1.Particle size <0.5 <1 <0.5 0.4    (micron)  2. Particle <0.5 <1 0.3-0.5<0.6    distribution    (micron)  3. Particle Irregular irregularirregular irregular    morphology  4. Powder Freeze-dry Wet chemistryGrinding Spray-dry    production granulation precipitation Freeze-drygranulation granulation  5. Crystal 98% alfa Apatite alfa tetragonal   structure 2% beta (hexagonal)  6. Theoretical 3.18 (batch 1, 2) 3.15g/cm³ 3.98 (batch 1)    density (g/cm³) 3.27 (batch 3) 3.79 (batch 2)3.12 (batch 4) 3.98 (batch 3) 3.79 (batch 4) 6.07  7. Apparent 0.38 0.60.5-0.8 —    density (g/cm³)  8. Melt 1800 1600 2050 2500-2600   temperature (° C.)  9. Sintering 1820 900 1600-1650 1500   temperature(° C.) 10. Hardness 1570 450 1770 1250-1350    (HV)17. Theoretical Density Study

FIG. 33 shows maximum obtained relative density as a function oftheoretical density for different metal powders. TABLE 23 ConditionsPressure Atmosphere Temperature Room temperature Energy retention NoMaterial Metal powder (see table 3)Result

The diagram shows a tendency that a metal powder with a high theoreticaldensity is more difficult to process with DFIER to a high density,compared with a metal powder with a low theoretical density. In table 1the materials used in the study are listed together with theoreticaldensities and obtained relative density for each material.

It is clear that many parameters are involved to decide if a material iseasy to process with DFIER to high densities. Other important powderproperties are powder type, alloying elements, powder hardness, meltingtemperature, particle size and particle morphology.

18. Powder Hardness Study

FIG. 34 shows maximum obtained relative density as a function of powderhardness for different ceramic and metal powders, respectively. TABLE 24Conditions Pressure Atmosphere Temperature Room temperature Energyretention No Material Metal powders (see table 3) Ceramic powders (seetable 4)Result

The diagram shows that it is more difficult to process a hard metalpowder to a high density compared with a soft powder using DFIER. Theplotted test values for metal powder has a smaller inclination comparedwith the values for ceramic materials. The diverging value (400 HV,70.6%) for the ceramic material is because it is a water based ceramic.This explains the low powder hardness.

A hard metal or ceramic powder can be processed in vacuum and increasedsurrounding temperature to reach higher densities.

19. Melting Temperature Study

FIG. 35 shows maximum obtained relative density as a function of meltingtemperature for different metal and ceramic powders, respectively. TABLE25 Conditions Pressure Atmosphere Temperature Room temperature Energyretention NoResult

The metal curve shows that there is no clear relation between themelting temperature for a metal and how easy it is to process with DFIERto high densities. Table 26 shows two steels with the same meltingtemperature but different powder hardness, which explains that only onematerial property cannot decide if the material is easy to process tohigh densities with DFIER. TABLE 26 Material type Powder hardness (HV)Melting temperature (° C.) Stainless steel 160-190 1427 Martensiticsteel 180-330 1427

Ceramic powders have higher melting temperature and are also moredifficult to process to high densities compared with metal powders,which is showen in FIG. 35.

20. Vibratory Compacting Study

FIG. 36 shows relative density as a function of applied pressure forsamples processed with conventional static pressing compared withsamples processed with vibratory compacting (VC) in combination withother processes. TABLE 27 Conditions Pressure Atmosphere TemperatureRoom temperature Material Stainless steel Vibrating velocity 233oscillations/s Shock energy 300-3000 NmResult

The curves show that relative density of powders vibrated undercontrolled conditions during a static pressure or/and in combinationwith shock energy reach much higher densities compared with samplesprocessed with only static pressure.

Samples compacted with vibratory compacting, shocked from two directionsand with double axial static pressure reaches the highest density forthe lowest total pressure.

1. A method of producing a body from particulate material by coalescenceor compaction to higher density, characterised in that the methodcomprises the steps of a) filling a pre-compacting mould with thematerial in the form of powder, pellets, grains or the like, b)vibrating the mould, c) pre-compacting the material at least once with apre-compacting means and d) compressing the material in a compressionmould by at least one stroke, where a striking unit emits enough kineticenergy to form the body when striking the material inserted in thecompression mould with a striking means, causing coalescence or higherdensity of the material.
 2. A method according to claim 1, characterisedin that the pre-compacting mould and the compressing mould are the samemould.
 3. A method according to claim 1, characterised in that thepre-compacting c) is performed while vibrating the mould.
 4. A methodaccording to claim 1, characterised in that d) the material iscompressed from two opposite sides simultaneously using two strikingunits.
 5. A method of producing a body from solid material bycoalescence or compaction to higher density, characterised in that themethod comprises the steps of a) inserting the solid material in amould, c) possibly pre-compacting the material at least once with apre-compacting means and d) compressing the material in the mould by atleast one stroke, from two sides simultaneously, using two strikingunits emitting enough kinetic energy to form the body when striking thematerial, causing coalescence or higher density of the material.
 6. Amethod according to claim 1, characterised in that the material iscompressed from two opposite sides and at least one further sidesimultaneously using at least three striking units.
 7. A methodaccording to claim 2, characterised in that the pre-compacting means iscontinuously applied against the material with the same or a higherpressure during the compression d) thereof with the striking unit orunits.
 8. A method according to claim 1, characterised in that theenergy of the compression d) is retained within the compressed materialby e) maintaining or reapplying the striking means to press against thecompressed material after the stroke or strokes.
 9. A method accordingto claim 1, characterised in that the temperature of the material in themould is increased or decreased during one or more steps.
 10. A methodaccording to claim 9, characterised in that the material in the mould isheated before and/or during the pre-compaction c.
 11. A method accordingto claim 9, characterised in that the material in the mould is heatedbefore and/or during the compression d).
 12. A method according to claim10, characterised in that the material in the mould is heated by the useof electrical current.
 13. A method according to claim 12, characterisedin that the electrical current flow is syncronized with thepre-compaction c) and/or the compression stroke or strokes d).
 14. Amethod according to claim 1, characterised in that the material in themould is subjected to a sub-atmospheric pressure before thepre-compaction c).
 15. A method according to claim 1, characterised inthat the material in the mould or moulds is maintained under another gasthan air.
 16. A method according to claim 15, characterised in that thegas is an inert gas.
 17. A method according to claim 15, characterisedin that the gas is a reactive gas.
 18. A method according to claim 1,characterised in that the vibration b) is maintained during compressingd) and/or during energy retention e).
 19. A body produced by the methodaccording to claim
 1. 20. A method according to claim 5, characterisedin that the material is compressed from two opposite sides and at leastone further side simultaneously using at least three striking units.